bmp保存灰度图

转自：http://m.blog.csdn.net/g200407331/article/details/52540478，亲测可行

灰度图像数据存在一块内存里，首地址为pData,宽度为iWidth,高度为iHeight，保存路径为qstrPath

由于bmp的第一行像素代表的其实是图像的最后一行像素，所以向bmp文件写入像素时，其实是倒着写

void vSaveImg(unsigned char * pData, int iWidth, int iHeight, QString qstrPath)
{
	BITMAPFILEHEADER targetfileheader;
	BITMAPINFOHEADER targetinfoheader;
	memset(&targetfileheader, 0, sizeof(BITMAPFILEHEADER));
	memset(&targetinfoheader, 0, sizeof(BITMAPINFOHEADER));

	targetfileheader.bfOffBits = (DWORD)sizeof(BITMAPFILEHEADER) + (DWORD)sizeof(BITMAPINFOHEADER) + 256 * sizeof(RGBQUAD);
	targetinfoheader.biSize = iWidth * iHeight + sizeof(RGBQUAD) * 256 + sizeof(BITMAPFILEHEADER) + sizeof(BITMAPINFOHEADER);
	targetfileheader.bfReserved1 = 0;
	targetfileheader.bfReserved2 = 0;
	targetfileheader.bfType = 0x4D42;

	targetinfoheader.biBitCount = 8;
	targetinfoheader.biSize = sizeof(BITMAPINFOHEADER);
	targetinfoheader.biHeight = iHeight;
	targetinfoheader.biWidth = iWidth;
	targetinfoheader.biPlanes = 1;
	targetinfoheader.biCompression = BI_RGB;
	targetinfoheader.biSizeImage = 0;
	targetinfoheader.biXPelsPerMeter = 0;
	targetinfoheader.biYPelsPerMeter = 0;
	targetinfoheader.biClrImportant = 0;
	targetinfoheader.biClrUsed = 0;

	RGBQUAD rgbquad[256];
	int i;
	for(i = 0; i < 256; i++)
	{
		rgbquad[i].rgbBlue = i;
		rgbquad[i].rgbGreen = i;
		rgbquad[i].rgbRed = i;
		rgbquad[i].rgbReserved = 0;
	}

	
	FILE * fp = fopen(qstrPath.toLatin1().data(), "wb");
	fwrite(&targetfileheader, sizeof(BITMAPFILEHEADER), 1, fp);
	fwrite(&targetinfoheader, sizeof(BITMAPINFOHEADER), 1, fp);
	fwrite(&rgbquad, sizeof(RGBQUAD), 256, fp);
	
	for(i = 0; i < iHeight; i++)
	{
		fwrite(pData + (iHeight - 1 - i) * iWidth, iWidth, 1, fp);
	}
	fclose(fp);
}